softirq: A single rcu_bh_qs() call per softirq set is enough
Calling rcu_bh_qs() after every softirq action is not really needed.
What RCU needs is at least one rcu_bh_qs() per softirq round to note a
quiescent state was passed for rcu_bh.
Note for Paul and myself : this could be inlined as a single instruction
and avoid smp_processor_id()
(sone this_cpu_write(rcu_bh_data.passed_quiesce, 1))
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
diff --git a/kernel/softirq.c b/kernel/softirq.c
index b50990a..b9b2d49 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -232,7 +232,6 @@
bool in_hardirq;
__u32 pending;
int softirq_bit;
- int cpu;
/*
* Mask out PF_MEMALLOC s current task context is borrowed for the
@@ -247,7 +246,6 @@
__local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
in_hardirq = lockdep_softirq_start();
- cpu = smp_processor_id();
restart:
/* Reset the pending bitmask before enabling irqs */
set_softirq_pending(0);
@@ -276,11 +274,11 @@
prev_count, preempt_count());
preempt_count_set(prev_count);
}
- rcu_bh_qs(cpu);
h++;
pending >>= softirq_bit;
}
+ rcu_bh_qs(smp_processor_id());
local_irq_disable();
pending = local_softirq_pending();
